[Evolution] How does Evolution open a URL in a new tab in firefox?

[Van Snyder <van snyder sbcglobal net>]

How does Evolution open a URL in a new tab in firefox?

I can't do it from the command line. Online discussion says to use the "--new-tab" command-line option, but firefox always puts up a window saying it's already running, and inviting me to create a new profile.

I have other applications for which Id like to open a new tab (or new window), not start another instance of firefox, such as kalarm.

Dolphin can do it too. Nautilus can do it.

How does Evolution (or dolphin or nautilus) do it?